As far as I can tell, “plastics” is simply the plural of the word plastic used as a noun. In the case you mention I would use plastics since there may be many different plastics involved. Plastic is an old word and predates what we call plastic. My brother, a PhD computer professor, uses the word plastic to mean fake or imitation. He is against all things plastic. Plastics have revolutionized our culture and some is not for the best. Do you know about the plastic sea in the middle of the Pacific? It is where all bad plastics go when they die. It is about the size of Texas. This isn't a joke but it may be an exaggeration with a weird poetic twist.

The Collins Cobuild Dictionary says that "plastic" is a Mass Noun and the front matter of the dictionary says that mass nouns "typically combines the behaviour of both count and uncount nouns in the same sense. It is used like an uncount noun to refer to a substance. It is used like an count noun to refer to a brand or type."

By using "plastics technology" the company wants us to note that it is not using "plastic" as an adjective to modify "technology." As a adjective, it would have a meaning as described by Mr Hudson, and the company would naturally want to avoid that idea.

On the other hand, by using "plastics," the phrase now has a noun-noun structure and emphasizes the range of different plastic types with which the company can work.

Under the circumstances, "plastics technology" is probably the better choice. But as Slava points out, the final choice will depend on the context.